Profilin

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Profilin (blue) in complex with actin (green). (PDB code: 1BTF)
Profilin is an actin-binding protein involved in cytoskeleton dynamics. It is found in most eukaryotic cells and in mammalian cells two kinds of profilin have been discovered; Profilin I and II. Profilin I is expressed in most tissues except skeletal muscle, heart and brain, and profilin II expressed in brain, skeletal muscle and kidney.[1] In general, profilin is responsible for the growth and stabilization of actin filaments and is important in the restructuring of microfilaments. This restructuring of the actin cytoskeleton is used by the cell to allow the cell to move, and to adjust its shape according to its needs. Profilin was described by Carlsson et al. in 1976, and was the first protein component established to be necessary for actin reorganisation in cells.

Mechanisms of enhancing actin growth

Profilin enhances actin growth in two ways.
  • Profilin binds to monomeric actin on the plus end of the filament inducing a shape change of the actin subunit, allowing the G-actin to replace the ADP to which it is bound by ATP and form F-actin. The F-actin then forms a heterodimer which can bind to the plus end of an Actin filament. In the process of binding to the actin monomers it also stereochemically inhibits addition to the - end.
  • Secondly, following a conformational change in actin, profilin dissociates and competes for monomers with the inhibitory thymosin which sequesters the actin. Profilin is found in the cytosolic phase of the cell membrane where it can recruit monomers to grow filaments from the cortex.

Regulation

Profilin acts to regulate polymerization of actin monomers by sequestering G-actin. Profilin binds to minus ends of an actin subunit. Thymosin beta4 binds G-actin that profilin released and prevents it from binding to the plus end of a filament and thereby removing it from the concentration of the pool of free monomers that can form filaments. Thymosin beta4 can regulate concentration of ATP bound monomers and therefore the amount of actin polymerization in the cell as polymerization of these monomers requires the release of profilin from actin monomer.[2]

Profilin can also regulate polymerization by binding to the ends of the actin filaments rather than the monomers <ref name="Witke" />. Once the actin/profilin complex has formed, phosphoinositides can break the complex apart, releasing the ATP bound monomer and inducing polymerization. [3]

PIP2 has also been determined to be a regulatory mechanism on profilin, regulating the association of profilin with actin.[4]

Effects on cofilin

Profilin acts to reverse the effects of cofilin, an actin depolymerization factor that binds to actin filaments resulting in an increase in dissociation of monomers from the polymer. The cofilin stays associated with actin monomers and prevents reassembly. When profilin binds to G-actin, the subunit will dissociate from cofilin after an exchange of ADP for ATP.

Genes

References

1. ^ Witke, W., Podtelejnikov, A., Di Nardo, A., Sutherland, J., Gurniak, C., Dotti, C., and M. Mann (1998) In Mouse Brain Profilin I and Profilin II Associate With Regulators of the Endocytic Pathway and Actin Assembly. The EMBO Journal 17(4): 967-976 Entrez PubMed 9463375
2. ^ Actin Cytoskeleton
3. ^ Plank, L., and B. Ware (1987) Acanthamoeba Profilin Binding to Fluorescein-Labeled Actins. Biophysical Journal 51: 985-988 Entrez PubMed 3607215
4. ^ Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K. and Walter, P. (2002) The Molecular Biology of Cell. Garland Science Textbooks.
5. Carlsson, L. et al. 1976 J. Mol. Biol. 105:353-366. 6. Carlsson, L. 1979 Cell Motility. The possible prole of unpolymerized actin. Acta Universitatis Upsaliensis 537

External links

This is a list of actin-binding proteins in alphabetical order.
List: 0–9 A B C D E F G H I J K L M N O P Q R S T U V W x Y Z
References  External links

0–9

  • 25kDa
  • 25kDa ABP from aorta p185neu

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cytoskeleton is a cellular "scaffolding" or "skeleton" contained, as all other organelles, within the cytoplasm. It is contained in all eukaryotic cells and recent research has shown it can be present in prokaryotic cells too.
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Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

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Biological tissue is a collection of interconnected cells that perform a similar function within an organism.

The study of tissue is known as histology, or, in connection with disease, histopathology.
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Skeletal muscle is a type of striated muscle, usually attached to the skeleton. Skeletal muscles are used to create movement, by applying force to bones and joints; via contraction.
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heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in the annelids, mollusks, and arthropods.
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In animals, the brain or encephalon (Greek for "in the skull"), is the control center of the central nervous system, responsible for behavior. The brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing,
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The kidneys are organs that filter wastes (such as urea) from the blood and excrete them, along with water, as urine. The medical field that studies the kidneys and diseases of the kidney is called nephrology[1].
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Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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Thymosin is a hormone secreted from the thymus. Its primary function is to stimulate the production of T cells, which are an important part of the immune system.

Thymosin also assists in the development of B cells to plasma cells to produce antibodies.
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PIP2 or Phosphatidylinositol bisphosphate is general term that refers to the products obtained by cleavage of PIP3.

PIP2 is a substrate for clevage with phospholipase C, a membrane-bound enzyme activated throguh α1 adrenergic receptors.
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Identifiers
Symbol CFL2

Entrez 1073
HUGO 1875
OMIM 601443

RefSeq NM_021914
UniProt Q9Y281
Other data

Locus Chr. 14 ADF/cofilin is a family of actin-binding proteins which disassembles actin filaments.
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The EMBO Journal is a scientific journal focusing on full-length papers describing original research of general interest in molecular biology and related areas. It is one of the most influential journals in its field. The 2004 impact factor was 10.456.
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The Entrez Global Query Cross-Database Search System is a powerful federated search engine, or web portal that allows users to search many discrete health sciences databases at the National Center for Biotechnology Information (NCBI) website.
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The Biophysical Journal is published by the Biophysical Society. The society comprises chemists, biochemists, and physical chemists, biologists, neuroscientists, plant and animal physiologists, engineers, mathematicians, and physicists.
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The Entrez Global Query Cross-Database Search System is a powerful federated search engine, or web portal that allows users to search many discrete health sciences databases at the National Center for Biotechnology Information (NCBI) website.
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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cytoskeleton is a cellular "scaffolding" or "skeleton" contained, as all other organelles, within the cytoplasm. It is contained in all eukaryotic cells and recent research has shown it can be present in prokaryotic cells too.
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Microfilaments are the thinnest filaments of the cytoskeleton found in the cytoplasm of all eukaryotic cells. These linear polymers of actin subunits are flexible and relatively strong, resisting buckling by multi-piconewton compressive forces and filament fracture by nanonewton
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Actin is a globular structural, 42-47 kDa protein found in many eukaryotic cells, with concentrations of over 100 μM. It is also one of the most highly conserved proteins, differing by no more than 5% in species as diverse as algae and humans.
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This is a list of actin-binding proteins in alphabetical order.
List: 0–9 A B C D E F G H I J K L M N O P Q R S T U V W x Y Z
References  External links

0–9

  • 25kDa
  • 25kDa ABP from aorta p185neu

..... Click the link for more information.
Actinin is a microfilament protein. α-Actinin is necessary for the attachment of actin filaments to the z-line membrane, in muscle cells. The functional protein is an anti-parallel dimer, which cross-links the thin filaments in adjacent sarcomeres, and therefore coordinated
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Arp2/3 complex is a seven-subunit protein that plays a major role in the regulation of the actin cytoskeleton. It is a necessary component of the actin cytoskeleton and is therefore ubiquitous in actin cytoskeleton-containing eukaryotic cells.[1].
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Identifiers
Symbol CFL2

Entrez 1073
HUGO 1875
OMIM 601443

RefSeq NM_021914
UniProt Q9Y281
Other data

Locus Chr. 14 ADF/cofilin is a family of actin-binding proteins which disassembles actin filaments.
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Destrin is a protein in microfilaments.

External links

  • MeSH Destrin


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Gelsolin is an actin-binding protein that is a key regulator of actin filament assembly and disassembly. Gelsolin is one of the most potent members of the actin-severing gelsolin/villin superfamily, as it severs with nearly 100% efficiency.
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Myosins are a large family of motor proteins found in eukaryotic tissues. They are responsible for actin-based motility.

Structure and Function

Domains

Most myosin molecules are composed of both a head and a tail domain.
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